View of The effect of seed size and depth of seeding on the emergence of grassland plants

THE EFFECT

OF SEED SIZE

AND DEPTH

OF

SEEDING

ON

THE EMERGENCE

OF GRASSLAND

PLANTS

K. Multamäki

Agricultural Research Centre, Department

of

^{Plant Breeding,}

Jokioinen

Received November^{22, 1961}

The seeding of grasslands in Finland fails relatively often owing to ^the diffi- cult growing conditions for the young seedlings.^{As a}result, ^{the stands} are in many cases rather thin ^and must sometimes be ploughed up without giving any yield

at all.

One of the factors hampering ^the initial growth and development of grass- land plants is unsuitable sowing. Thus, for instance, ^aconsiderable proportion of the seed may ^{be sown} at too great a depth, ^whichprevents the seedlings from emerging. ^{On the} other hand, ^the seeds scattered ^{upon the} soil surface will also meet difficulties ⁱⁿ their germination stage, especially ⁱⁿ dry periods. Hence, a valuable characteristic^foragrassland plant seedling would^{be the}ability to surmount the various obstacles arising from deficient seeding ^measures.

The object ofthe present investigation is to study the emergence capacity of some grassland plants, ^the majority of which are grown extensively ⁱⁿ Finland.

Forthis purpose, ^seeds of^the plants to ^be studied ^{were sownön}soil surface ^aswell as at different depths. ^The influence of seed size in this connexion ^was examined, too. All the ^studies concerned ^were carried out ^{in the} greenhouse. ^{The soil}used as substrata in these experiments was heavy clay, representing the valuable arable

soil type occurring fairly commonly, especially in Southwest Finland.

Review of ^literature

Murphyand^Arny(4) found depth of planting to be the most important factor determining ^{the total}emergence of seedlings ^of various grasses andlegumes. ^The seed weight ^showed a significant positive correlation with ^the total emergence.

In alfalfa, ^Erickson (1) observed ^that both germination^andvigour of^the seedlings were directly correlated ^with seed size. Seedling vigour ^was inversely related to the depth of seeding. ^Rogler (5) established highly significant differences ^{in total}

19

seedling emergence for depths, weights, and the interaction of depths and weights in crested wheatgrass. McKenzie et al. (3) and Lueck et al. (2), found that the maximum depth of seeding varied considerably according to ^the grass species and varieties studied.

Material and methods

Few of theplant species ^andnone ofthe varieties tested in these experiments, however, are used in grassland cultivation ⁱⁿ Finland. ^Acorresponding experiment with plant material ^morefamiliar ⁱⁿ Finnish conditions ^{was thus} considered^appro- priate.

The following plant species and strains were included in^the experiment;

I red clover, diploid Tammisto, Finland

II ^{» *} tetraploid Jo ^{TPA 1}

111 alsike ^» diploid Jo ^{AA 10}

IV ^{* *} tetraploid Jo ^{TAA 4}

V white ^» Morso, Denmark

VI timothy Jo ^{Per. 38}

VII meadow fescue Paavo, Jokioinen VIII cocksfoot Pajbjerg 11,Denmark IX perejmial rye-grass Viris, Sweden

X Italian ^* Foreigncommercial seed

XI red fescue ^{» » »}

The strains for the experiment were selected ^from the breeding material of the Department ^{of Plant} Breeding at

Jokioinen

(marked Jo) ^as well as from ^com- mercial varieties and seed. ^{From each} of ^the strains ^{3 or 4} seed-size classes ^were separated by means of screening and hand sorting. The weight of the seeds was determined by taking an average of ^threeseparate lots of 200 seeds. All test seeds were treated with malathion preparation immediately before sowing. The normal germination capacity ^was analyzed ^{in the} ordinary ^way from 4 samples of ¹⁰⁰ seeds each.

For each of the tetraploid clovers and for timothy, four seed-size classes ^were taken; in another eight strains only three size classes ^were separated. The ^1000- seed weights in grams on the different seed-size classes of the eleven grassland plants studied were as follows:

Small Medium- Large Super-

sized sized

I Red clover, diploid 1.100 1.700 2.233

II ^» tetraploid 1.300 1.700 2.240 3.100

111 Alsike clover, diploid 0.550 0.691 0.917

IV ^» tetraploid 0.660 0.700 0.912 1.500

V White clover 0.483 0.626 0.933

VI Timothy 0.303 0.422 0.640 0.861

VII Meadow fescue 1.133 1.775 2.433

VIII Cocksfoot 0.583 0.783 1.066

IX Perennial rye-grass ^1.425 1.758 2.275

X Italian ^» 1.216 1.790 2.608

XI Red fescue 0.950 1.163 1.416

The heavy clay ^soilselected for ^this study^wastaken ^{from the}surface ²⁰centi- metres of the experimental field at

Jokioinen.

The soil concerned contained 4—5^% organic matter, its degree of acidity varying ^between pH ^5.5—5.9. Before ^use, the soil was air-dried and sieved in ^{orderto remove} lumps.

Seeding was done in cylindrical ^dishes measuring ^15cm in diameter and 9cm in height (Figure 1). ^The depths ^of planting used in this study were as follows:

surface, 1 cm, ^2.5cm, 4 cm,^and 7 cm. The planting depths^were determined ^ac- curately by ^means of wooden soil levellers. After seeding, ^{the soil was} kept at optimum moisturein orderto promote germination and emergenceof the seedlings.

The dishes _were kept ^{in the} greenhouse, ^{where the} temperature was main- tained at

+lB°

^{to +25° C by dayand at}

+l4°

^to

+lB°

^{C at night.}

The germination capacity ^{of the} different^seed-size classes proved to ^be very high, varying ^between 96 and 100 per cent. In each dish 100 seeds were sown.

Every seed-size ^class being ^planted at five depths ^with four replicates for ^each, was thus ^{grown in 20} dishes ⁱⁿ all. Notes ^on the emergence were recorded daily until no further seedlings appeared.

Experimental results

In order to gain ^an idea of the rate of emergence of the different strains in- vestigated, the average emergence of the medium-sized seeds from the 1-cm depth wascalculated for three-day periods. The^results are shown graphically in_Figure 2.

It appears that, on the whole, ^the legume seedlings (I—V) began to emerge more rapidly than the grass seedlings (VI —XI). ^In addition, ^the legumes often attained

total ^{emergence over a shorter} period ^of time than the grasses.

Between the individual strains some great differences are to be seen with

Figure ^1, Emergence of the large-sized seeds ^of Italian rye-grass from surface, 1-cm, 2.5-cm, and 4-cmdepths, 7daysafterseeding. Photoby^O,Inkilä,

21

regard to the rate of ^emergence. Thus, for example, the tetraploid red (II) ^and alsike (IV) clovers obviously emerged ^more slowly ^{than the} corresponding diploids (I ^and III). ^Besides this, the total emergence of the tetraploids proved to ^be less than that of the diploid strains.

From Figure ² it further appears that, among ^the grasses, ^the seeds of Italian rye-grass (X) began emerging^withexceptional rapidity. ^In timothy (VI), cocksfoot

Figure 2. Rate of emergence of medium-sized seeds from I-cm depth. The eleven grassland plants I —XI listed under »Material and methods».

(VIII), and red fescue (XI), ^{on the other}hand, no emergence ^occurred during^the first three-day period. ^Therate of emergence of meadow fescue (VII) ^andperennial rye-grass (IX) ^was also ^slow at the outset.

Maximum ^{emergence was} usually reached from ⁹ to 12 days ^after seeding.

The emergenceof Italian rye-grass (X) wasnot complete until 15days after seeding.

In cocksfoot (VIII), total emergence ^was onlyattained in 18days; the rate ofemer- gence of this species ^was thus slowest in the categoryof medium-sized seeds sown at ^1-cm depth.

It ^was further established that rate of ^{emergence was} considerably retarded with increasing depth. As ^aresult of deeper sowing, ^the time required ^for complete emergencewasdistinctly prolongedin manyofthestrains studied. Thus,for example,

Table 1. Average seedlingemergence from 100 seeds of eleven grassland plants of different weight

Grassland Seed size Variation due

plant to seed size

Small Med. Large Super D.F. F value

I Red clover, dipl. 47 54 47 2 3.08

II ^{» tetr.} 34 44 52 55 3 11.7*»*

111 Alsike cl., dipl. 63 65 67 ^- 2 1.72

IV ^* tetr. 53 55 61 64 3 7.2***

V White clover ^{40 51} 57 ^- 2 44.0***

VI Timothy 40 54 57 71 3 1103.2***

VII ^Mead, fescue 44 49 65 2 23.9***

VIII Cocksfoot 57 55 62 2 2.19

IX Per. rye-grass ⁷⁰ 72 74 2 1.79

X Ital. ^» 72 75 77 ^- 2 ^6.79**

XI Red fescue 51 57 56 2 1.97

Grand average ^{52 67 61 63}

classessown at five depths, as well as theanalyses ofvariance of seed ^sizeand depth of seeding

Depth of seeding, Variation due Size x

cm to depth depth

of seeding interaction

0 1 2.5 4 7 D.F. F value D.F. F value

78 63 48 41 16 4 56.4*** 8 3.44**

79 52 54 36 12 4 65.0*** 12 2.85*»

85 85 77 77 1 4 247.0*** 8 1.14

87 78 78 45 3 4 266.8*** 12 2.55**

64 64 62 54 1 4 283.0*** ^{8 5.54***}

80 91 79 29 1 4 8372.6*** 12 377.7***

62 73 65 32 33 4 43.0*** 8 0.54

82 85 70 46 8 4 99.3**» 8 1.07

82 92 91 88 7 4 414.4*** 8 0.71

92 93 95 89 7 4 817.6*»* 8 3.34»*

74 ⁶⁴ 58 54 5 4 86.8*** ⁸ 0.96

79 76 71 54 9 ^-

23

the totalemergenceof meadow fescue (VII), perennial rye-grass (IX), and^red fescue (XI) sownat7-cmdepth^wasnot reached until 21days after seeding, the correspond- ing times at ^1-cm depth being 12, 9, and ¹² days.

The data on the ^average total emergence are shown in Table 1, which also contains ^theresults ofthe corresponding analyses of variance.From the data thus presented, it^ispossible to gain ^anidea ^{of the} significance of^seedsize^{and of}different depths of sowing ^{on emergence capacity.}

In the diploid red and ^alsike clover seed size proved to have no significant influence^{on the} differencesin emergencecapacity. ^In the corresponding tetraploids, however, ^seedsize proved to ^be highly significant. ^In four ^{of the}remaining seven species ^distinct dependence ^{of total} emergence upon ^{seed size was} established, too.

These were: white clover, timothy, ^meadow fescue, and Italianrye-grass. In cocks- foot, perennial rye-grass and red fescue, on the otherhand, no significant relation- ship was found.

As regards depth of seeding (Table 1), highly significant effects of this factor on the emergence capacity^were established in all eleven strains investigated. The importance ^ofdepth^of seeding ^thus appeared to^be greater ^{than that}of^{seed size.}

The ^numbers of seedlings emerging from different depths ^show very considerable differences. ^{In the} tetraploid clovers, timothy, ^meadow fescue ^and cocksfoot, seeding 4cm deep already markedly impaired ^emergence. At 7 cm the seedlings’

chancesof becoming established wereappreciably weakened. ^Thediploid and tetra- ploid alsike clover, white clover and timothywere the most sensitivein this respect.

Of^the eleven strains investigated only^meadowfescue ^was able to^emerge passably from ^a depth of ^{7 cm.}

In addition, statistical analysis of the data indicates significant interaction for the sizes x depthsⁱⁿ four legumes ^and two grasses (Table 1). This result reveals thatⁱⁿ thesestrains therearereal differences in the emergencecapacity ^ofseedlings of various weight classes seeded at different depths. On ^the other hand, ^{in one} legume ^andfour grasses no such interaction could be established with certainty.

Discussion

Because the moisture conditions in the disheswere continuously kept at opti- mal level, the emergence figures obtained ⁱⁿ this experiment are obviously much higher ^{than those} found ⁱⁿ natural conditions. This is especially true in ^the case ofthe surface seedings; seedlings situated ^{on the} soil surface in the field are more exposed to drought injury ^{than those} within ^the soil.

The legumes, ⁱⁿ most cases, began emerging ^{from 1-cm} depth more rapidly than the grasses. Further, ^the legumes ^reached total emergence from this depth on an average three daysbefore the grasses (Fig. 2). Thisresult is in accordance with ^thefindings of^{Murphyand Arny}(4),^whoreported asimilarrelation between the rates ofemergenceof five legumes and five grasses. The rapid emergenceof^the legumes is an evident advantage. Thus, at ^the establishment of ^aley ^the legumes are obviously ⁱⁿ need of favourable conditions for emergence for ^a shorter period of ^time after seeding ^{than the} grasses.

The emergence capacity ^of the tetraploid clovers (II and IV) seems to be weaker than that of the corresponding diploids (I and III); (Fig. 2 and Table 1).

This finding, however, ^maynot ^be generally applicable. Both thetetraploid clover strains investigated,

Jo

TPA 1 red clover and

Jo

TAA 4 alsike clover, are rela- tively newly produced strains ^{that have} obviously not yet^reachedcomplete physio- logical balance. ^It is to be expected, therefore, that as aresult of continued breed- ing their emergence capacity will improve essentially.

Comparison of the influence of seed size and the depth ^of seeding ^{on emer-} gence (Table 1) reveals that the average emergence figures for ^the four seed-size classes differ from^one another relatively little. Further, in five of the eleven strains studied, no significant dependence of total emergence upon seed size was found.

The average emergence figures at different seeding depths, ^{on the} contrary, varied considerably. ^{The effect} upon emergence ^{of the} depth^of seeding proved also to ^be highly significant ^{in all} strains.

The ^average figures of emergence from seedings ^{made on the} soil surface and at depths of ¹ and 2.5 cm w'ere about equally high (Table 1). Emergence ^from a depth ^{of 4 cm, on the other} hand, was considerably lower than in the above-mem tioned cases. Even so, on an average ^{more than half}ofall the seeds of the different strains placed at ^a depth ^{of 4 cm, gave} rise to emerging seedlings. The emergence from this depth ^{of the} diploid alsike clover ^{and of the} two rye-grasses mayeven be considered ^very satisfactory. Finally, seeding at 7-cm depth gave rather poor emergence in all the strains examined, with the exception of meadow fescue.

Thus, under the conditions of this experiment, ^it appeared ^that 4 cm may be considered the maximum depth^{from which} most of^the strains studied ^are still able to give intermediate or satisfactory establishment (Table 1). The average emergence figures ^{of the} two most important grassland plants ^{in Finnish} leys, the diploid^red clover ^and timothy, ^were markedly reduced at^this depth^ofseeding, being 41 and ^29, respectively.

Conclusions

From 1-cmdepth ^ofseeding ^the legumes, ^{on the} whole, began to emergemore rapidly ^than the grass seedlings. Besides this, the legumes often attained total

emergence over a shorter period of time than the grasses.

Between the rates ^of emergence of the individual strains _some considerable differences ^were established. Maximum emergence from 1-cm depthwas generally reached from 9 to 12 days ^after seeding.

The rate ^of emergence ^was considerably ^retarded at greater depths. ^Corre- spondingly, ^{the time} required for complete emergence was distinctly prolonged ⁱⁿ many of the strains ^studied.

The influence of depth of seeding on the emergence of the eleven strains investi- gated proved to be greater ^{than that}of seed size. ^In four legumes and two grasses significant interaction for ^the sizes x depths was ascertained.

Under the conditions of the experiment, seeding at ^4-cm depth may ^{be con-} sidered ^the maximum depth ^of seeding ^for most ofthe strains investigated.

25

REFERENCES

(1) Erickson, ^{L. C.} 1946.The effect of alfalfa seed size and depth of seeding upon the subsequent procurement ofstand. J.Amer. Soc. Agron. 38;964—973.

(2)Lueck, A.G. ^& Sprague,V.G. ^&Garber, R. J. ^1949.The effects ofacompanion crop and depth of planting on theestablishment of smooth bromegrass, Bromus inermis,Leyss. Agron.

J. 41: 137-140.

(3) McKenzie, R. E. ^& Heinrichs, D. H.^& Anderson, L. J. ^1946.Maximum depth of seedingeight cultivated grasses. Scient. Agric. 26: 426 431,

(4) Murphy,R. P.^&Army,A.C.1939. The emergenceofgrass andlegume seedlings planted atdifferent depthsin five soil types. J.Amer. Soc. Agron. 31: 17 28.

(5) Rogler, G.A. ^1954, Seed size and seedling vigor in ^crested wheatgrass. Agron. J. ^{46:216 220.}

SELOSTUS:

SIEMENEN KOON JAKYLVÖSYVYYDEN VAIKUTUS NURMIKASVIEN ORASTUMISEEN

K. Multamäki

Maatalouden tutkimuskeskus,Kasvinjalosluslaitos, fokioineⁿ

Yhdentoista nurmikasvikannan siemenistä otettiin 3 tai4 siemenkokolajitetta, jotka kylvettiin orastumisastiaan joko pintaan, 1, 2.5, 4 tai 7 senttimetrin syvyyteen (kuva 1). Orastumisalustanakäy- tettiinlaitoksen ^koekentänmuokkauskerroksesta otettua aitosavimaata. Kuhunkin astiaankylvettiin

100 siementä. Erikokoisten siemenlajitteiden itämisprosentti vaihteli 96—100.

Pyrittäessä vertailemaan eri kantojen orastumisnopeutta laskettiin yhden senttimetrin syvyy- teen kylvettyjen keskikokoisten siementen orastumisluvut kolmipäiväisille ajanjaksoille ^{(kuva 2).}

Nurmipalkokasvien (I— V) siementaimet alkoivat yleensä orastua nopeammin kuin heinien (VI—XI) janeorastuivat keskimäärin kolme päiväälyhyemmässä^ajassakuin viimeksi mainitut. Tetraploidiset apilat (II ja IV) orastuivat hitaammin jaheikommin kuin vastaavatdiploidit (I jaIII). Tämä johtunee kuitenkin siitä, ettäkokeillut tetraploidiset kannat ovat keskeneräisiä jalosteita, joiden fysiologinen tasapaino ei vielä liene täysin vakiintunut.

Yhden senttimetrin syvyyteen kylvetyt siemenet ehtivätyleensä orastua täysin 9—12päivässä.

Italialaisella raiheinällä (X), joka aloitti orastumisensa erittäin nopeasti, kului täydelliseen orastumi- seen aikaa 15 päivää. Koiranheinä (VIII) orastui yhdensenttimetrin syvyydestä täysin vasta 18päi- vän kuluttua.

Kylvösyvyyden ^kasvaessa orastumisnopeus hidastui. ^Tästä johtuen lisääntyi useiden kantojen täydelliseen orastumiseen tarvittava aika tuntuvasti.

Erikokoisten ja eri syvyyteen kylvettyjen siemenien keskimääräisten orastumisprosenttien (tau- lukko 1) nojalla _onpääteltävissä,että kylvösyvyydellä ontärkeämpi merkitys orastumiselle kuin ^sie- menen koolla. Neljässä nurmipalkokasvissa jakahdessa heinässätodettiinsiemenen koon ja kylvösy- vyyden välillä tilastollisesti merkitsevä vuorovaikutus.

Kokeillussa aitosavimaassa voitaneen neljää senttimetriä pitäämaksimisyvyytenä, jostauseim- mat ^tutkitut kannat pystyivät vielä orastumaan keskinkertaisesti ^tai tyydyttävästi ^{(taulukko 1).}

Kahdentärkeimmän nurmikasvimme,diploidisen puna-apilansekätimotein orastaminen tästä syvyy- destä oli jo tuntuvasti vaikeutunut.